1. Field of the Invention
The invention relates to an article of footwear, such as a shoe, in particular a sports shoe, and more particularly a shoe structured and arranged for skiing, race walking, or for other athletics.
2. Background Information
Footwear of the aforementioned type can be used in fields such as cross-country or telemark skiing, walking or running on flat or mountainous terrain, hiking, snowboarding, snowshoeing, skateboarding, cycling, ball-playing sports, and in other fields of endeavor.
An article of footwear, or a shoe, can have a low upper or a high upper and can be relatively flexible or, conversely, more rigid. In any case, the shoe is provided with an outer sole assembly, which is adapted to connect the upper to the ground or to a sport apparatus.
In a known manner, the outer sole assembly can be made out of a synthetic material, such as plastic, molded or shaped using any technique. The outer sole assembly is thus an element that extends lengthwise from a rear end to a front end, widthwise between a lateral side and a medial side, and heightwise between a free surface, adapted to contact the ground or the sports apparatus, and a connection surface, adapted to be affixed to the upper.
This element has the advantage of being easy to manufacture. However, the use of only one material does not make it possible to optimize the mechanical properties of each subdivision of the outer sole assembly. Indeed, various zones are subject to stresses of different types. For example, certain zones work in fatigue, such as those located at the limit between the toes and the metatarsus. This is where repeated flexing of the foot causes repeated flexing of the sole assembly. Other zones, for example, work in compression or friction, such as the heel zone, for example. Other zones still can absorb specific steering forces. This is particularly the case in cross-country skiing, where the outer sole assembly includes one or more connecting members, each provided for reversibly connecting the shoe to a retaining device, itself associated with the ski.
Still in a known manner, it has therefore been provided to use a plurality of synthetic materials to make an outer sole assembly, the underlying idea being to optimize the mechanical properties of at least certain subdivisions of the outer sole assembly.
For example, the main portion, or core, of the outer sole assembly is covered in the area of the heel and on the side of the free surface by one or more pieces of wear-resistant synthetic material.
Bands applied in the flexion zone, i.e., between the toes and the metatarsus, are also noted. The bands are made of a material different from that of the core.
Subdivisions made of different plastic materials, depending upon whether they include or do not include a member for connecting to a retaining device, such as a ski binding, are also noted.
Generally speaking, the known outer sole assemblies, made of a plurality of synthetic materials, still have certain disadvantages.
First, their mechanical properties are not optimized in all of their subdivisions. For technical shoes with a rigid sole assembly, it is noted, for example, that the edges of the sole assembly are not flexible enough and that, for this reason, they do not adequately assume the shape of the upper when the latter is being adhesively bonded to the sole assembly. This makes the adhesive bonding difficult. In addition, certain areas of the sole assembly that are more central are not sufficiently rigid to transmit the steering impulses with precision. Also, fatigue strength, related to the repeated flexing, is sometimes insufficient.
Next, it appears that the mechanical structure, when sufficiently strong, is also rather complex. This is particularly the case in cross-country skiing, where a member for connecting to the binding is affixed to the remainder of the sole assembly via several elements. This enables the member to be reliably affixed, while however increasing the structural complexity and the manufacturing costs.
Furthermore, it appears that incipient separation or fractures occur in the known sole assemblies, at the junction of the various materials. In other words, the known outer sole assemblies are sometimes fragile.
Moreover, the sole assemblies including a plurality of various materials are sometimes rather heavy.